This radio was a bit ahead of its time when it was introduced, this was a first generation genuine pll and instead of being an IC like we see in modern radio's this was a pll circut comprised of various simple ic's and a variety of other diodes and resistors.
That would be the reason I surmise they, (UNIDEN) combined all the functions into one IC as the result is much more easy to replace in case of problems as well as the newer multi function IC's where much cheaper to produce.
The only thing I can suggest is to change the reference crystal and try to tune the vco to allow for the change!